1. Field of the Invention
This invention relates to an electronic/hydraulic control system for maintaining the orientation of a rock drill feed arm regardless of the movement of the rock drill boom. The intent of the control arrangement is to simplify drilling of parallel bores in a mine face.
2. DESCRIPTION OF THE PRIOR ART
A common method for breaking a mine or other tunnel involves the drilling of a plurality of parallel bores very near to each other in the middle of the end wall of the tunnel. A portion of these so called opening bores are charged while the other portion is left uncharged. Parallelism of the opening bores is a condition of successful blasting.
In rock drilling it is common to utilize a hydraulic boom for supporting and guiding the rock drill bit and its feeding device. The boom has a first portion which can move in several ways. Normally it can turn both in the vertical and horizontal planes and can be rotated about a longitudinal axis therethrough. A drill feed arm or second portion is attached to the end first portion of the boom and can be guided with respect to all three space axis. When the first portion of the boom is moved the position of the feed arm end and its direction of orientation are changed. If one desires to have the end of the feed arm remain in constant orientation when transferred from one bore to another the feed arm must be reoriented to maintain the desired parallel orientation. In order to maintain this parallelism prior art U.S. Pat. No. 3,462,103 issued Aug. 19, 1969 to R. Strom utilizes a purely hydraulic boom guiding arrangement for a rock drilling machine. The hydraulic cylinders are connected to a hydraulic pump which is responsive to the movement of hydraulic fluid as the boom moves and pumps such amounts of oil to the cylinders so that the feed arm end will always maintain its direction when the boom is turning.
It has been found that this system has several limitations. Due to leakage hydraulic fluid in the system there sometimes occurs a drifting movement of the feed arm end and consequently a lose of accuracy in maintaining parallelism. Furthermore there is no direct readout of the feed arm angle to insure the operator that parallelism is being maintained. In addition the purely hydraulic system does not lend itself to remote control operation. Also it is not possible to control a mining vehicle havin more than one hydraulic boom each with separate hydraulic circuits utilizing the method of U.S. Pat. No. 3,462,103.
U.S. Pat. No. 4,033,626 issued on July 5, 1977 to Dinkelbach discloses a remotely controlled tunneling machine. This system uses a laser beam and a computer to produce the desired tunnel profile. This system uses encoders or transmitters to produce output signals which indicate the displacement of the pivot arm about its axis. Also the control of the shaft position is implemented trough the use of electro hydraulic control elements or servovalves.
Other U.S. patents which disclose various electronic systems for mining and tunneling machines are U.S. Pat. Nos. 4,238,828; 4,228,508 and 4,254,993. None of the above patents disclose a method for electronically controlling the movements of a boom on a rock drilling machine. The present invention allows these movements to either be made manually or with a computer system automatically maintaining constant orientation of the feed arm. Various other movements of the feed arm can be preprogrammed into the computer to fully automate the drilling of the blast hole pattern.